1. Field of the Invention
This invention relates to a sintered conductor circuit board on which LSIs or chip components are mounted and through which they are mutually connected.
2. Description of the Prior Art
Recently, a reasonably large number of functions can be achieved using an electric circuit, and accordingly the electric circuit has become complicated, resulting in a considerable increase in the number of electronic parts. For this reason, circuit boards have also become complicated and have become required to be made compact. In order to settle these subjects, the wiring or circuit density has become increasingly higher and at the same time a tendency toward a multi-layered circuit board has come to be seen.
A conventional process of fabricating multi-layered circuit boards comprises chemically etching (or photoetching) a copper foil on a resin support to form a pattern, laminating a plurality of the patterned foil, making a hole through the laminate in its thickness direction, and plating the inner wall of the hole (through-hole) so that the layers of the laminate can be mutually connected.
Since the through-hole is made using a drill, it can have a diameter of about 300 .mu.m at best. Since also the layers are connected by plating, a severe precision is required for the positional precision between layers and the shape of the inner wall of the through-hole, where an increase in the number of the layer results in a poor yield. Increasing the number of the layers for the purpose of a higher circuit density may also result in an increase in the number of the through-hole that connects such layers, rather making the wiring space smaller. This brings about a difficulty for achieving a higher circuit density. In addition, industrial waste of an etchant or the like used during fabrication has been problematic. The fabrication also has required a lengthy process, resulting in a high fabrication cost.